Wheelchairs have been used for many years in order to provide assistance in transportation of handicapped persons. In some cases, the handicapped person may be a paraplegic or a quadriplegic. In such cases, the wheelchair constitutes an invaluable source of individual transportation.
Whether manually operated or motor-driven, wheelchairs typically include a wheel-supported base for rollably supporting a seat. The seat, in turn, typically includes a bottom portion for supporting the gist of the weight of the intended user and a backrest portion for supporting the back of the intended user. Over the passed recent years, powered wheelchairs in particular have incorporated various features aimed at assisting the handicapped individual in his or her pursuit of independent operation and movement. Accordingly, some individuals, such as paraplegics and quadriplegics may spend a considerable amount of time sitting in their wheelchairs.
One of the major problems encountered by wheelchair users, especially paraplegics and quadriplegics, is the necessity to shift or move the body weight with respect to the support provided by the wheelchair. Indeed, the continuous pressure of the body's weight on certain specific locations of the body such as that provided by the skeletal structure causes the supporting skin to lose circulation.
If a person sits in the same position in a wheelchair for a long period of time, pressure is continuously applied to the tissue on the buttocks, legs and/or back that is bearing the person's weight in that position. This not only leads to discomfort and even pain but may also lead to medical complications such as sores, ulcers or the like.
In order to provide shifting of their body weight from time to time, some paralysed individuals may have to resort to using a nurse or attendant to manually tilt the entire wheelchair or the seat portion of the latter backwards so that the occupant's weight is shifted and the pressure points on the occupant's body is moved. However, body weight shifting is recommended at intervals of at least every 20 minutes.
This may prove to be a considerable task for a nurse or attendant. Furthermore, it would be more desirable to provide the wheelchair user with a means to make this shift of position on their own without assistance from an attendant.
It would, hence, be desirable to provide a reclining wheelchair in which the seat of the wheelchair is pivotally supported on the base of the wheelchair. The pivoting of an occupant with respect to the base would facilitate blood circulation, thereby providing relief for the occupant.
To address this problem, wheelchairs are sometimes provided with a movable pivot point upon which the wheelchair seat is mounted. Typically, a linear-type actuator is provided to raise the front end of the seat and tilt the seat back. However, prior art structures typically suffer from numerous drawbacks. One such drawback is that some prior art structures require the seat of the wheelchair be elevated to meet this demand since the actuating mechanism and associated linkage structures are relatively bulky. Wheelchair occupants typically disfavor this increase in elevation of the seat.
Another disadvantage associated with some prior art wheelchair tilting assemblies is that their configuration is such that, as the seat is reclined, the center of gravity for the occupied wheelchair shifts rearwardly. This shift of the center of gravity increases the tendency of the wheelchair towards rearward overturn. A significant shift in the center of gravity may even result in an unstable condition in which the force of gravity alone acting on the occupant is sufficient to overturn the wheelchair.
Accordingly, there exists a need in the industry for an improved seat supporting assembly and wheelchairs including same.